Field of the Invention
This invention relates in general to communication devices and in particular to an overvoltage suppressor construction and to a thermoprotection devcie therefore.
A similar thermal protection device is known from DE No. 27 38 078 A1. Therein, a melt element is formed as a sleeve surrounding the overvoltage suppressor, the sleeve being pierced by the arms of a U-shaped bow-type spring in case of an overvoltage. It is disadvantageous, that the melt element is an additional component, needing, further, to be adapted accurately to the shape of the overvoltage suppressor. Moreover, creepage currents between the arms of the bow-type spring and the contacts of the overvoltage suppressor may occur.
Further, a thermal protection device of a different type is known from EP No. 0.040.522 A1, wherein the overvoltage suppressor is not mounted in a chamber of the case body. Instead, pan-type melt elements are disposed, for accommodating compression springs of an overvoltage, the bottom sections of the pan-type melt elements will melt, and also the springs connecting the yoke-type contact plates to each other. In case of an overvoltage, the bottom sections of the pan-type elements will melt, and the springs connect the yoke-type contact plates to each other. It is disadvantageous, that the pan-type melt elements are additional components.
Further, from the bulletin "Surge Arresters" of the M-O Valve Company Ltd., a thermal protection device of overvoltage suppressor is known. This device is provided with a fixed spring rod held spaced from the overvoltage suppressor by means of a plastic coating. In case of an overvoltage, the plastic coating will melt, whereby the spring rod will short-circuit over the contacts of the overvoltage suppressor. It is disadvantageous that the spring rod is a special component fixed to the overvoltage suppressor, and the overvoltage suppressor cannot be reused after the plastic coating becomes molen.